linux-kernel - Re: [PATCH v15 09/13] tsc: Use the GUEST_TSC

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Message-ID: <20241230112904.GJZ3KEAAcU5m2hDuwD@fat_crate.local>
Date: Mon, 30 Dec 2024 12:29:04 +0100
From: Borislav Petkov <bp@...en8.de>
To: Nikunj A Dadhania <nikunj@....com>
Cc: linux-kernel@...r.kernel.org, thomas.lendacky@....com, x86@...nel.org,
	kvm@...r.kernel.org, mingo@...hat.com, tglx@...utronix.de,
	dave.hansen@...ux.intel.com, pgonda@...gle.com, seanjc@...gle.com,
	pbonzini@...hat.com
Subject: Re: [PATCH v15 09/13] tsc: Use the GUEST_TSC_FREQ MSR for
 discovering TSC frequency

On Tue, Dec 03, 2024 at 02:30:41PM +0530, Nikunj A Dadhania wrote:
> Subject: Re: [PATCH v15 09/13] tsc: Use the GUEST_TSC_FREQ MSR for...

The tip tree preferred format for patch subject prefixes is
'subsys/component:', e.g. 'x86/apic:', 'x86/mm/fault:', 'sched/fair:',
'genirq/core:'. Please do not use file names or complete file paths as
prefix. 'git log path/to/file' should give you a reasonable hint in most
cases.

Audit your whole set pls.

> +void __init snp_secure_tsc_init(void)
> +{
> +	x86_platform.calibrate_cpu = securetsc_get_tsc_khz;
> +	x86_platform.calibrate_tsc = securetsc_get_tsc_khz;

The fact that you assign the same function to two different function ptrs
already hints at some sort of improper functionality split.

> diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
> index 67aeaba4ba9c..c0eef924b84e 100644
> --- a/arch/x86/kernel/tsc.c
> +++ b/arch/x86/kernel/tsc.c
> @@ -30,6 +30,7 @@
>  #include <asm/i8259.h>
>  #include <asm/topology.h>
>  #include <asm/uv/uv.h>
> +#include <asm/sev.h>
>  
>  unsigned int __read_mostly cpu_khz;	/* TSC clocks / usec, not used here */
>  EXPORT_SYMBOL(cpu_khz);
> @@ -1515,6 +1516,10 @@ void __init tsc_early_init(void)
>  	/* Don't change UV TSC multi-chassis synchronization */
>  	if (is_early_uv_system())
>  		return;
> +
> +	if (cc_platform_has(CC_ATTR_GUEST_SNP_SECURE_TSC))
> +		snp_secure_tsc_init();

diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
index aac066d798ef..24e7c6cf3e29 100644
--- a/arch/x86/coco/sev/core.c
+++ b/arch/x86/coco/sev/core.c
@@ -3287,6 +3287,9 @@ static unsigned long securetsc_get_tsc_khz(void)
 
 void __init snp_secure_tsc_init(void)
 {
+	if (!cc_platform_has(CC_ATTR_GUEST_SNP_SECURE_TSC))
+		return;
+
 	x86_platform.calibrate_cpu = securetsc_get_tsc_khz;
 	x86_platform.calibrate_tsc = securetsc_get_tsc_khz;
 }
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index c0eef924b84e..0864b314c26a 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1517,8 +1517,7 @@ void __init tsc_early_init(void)
 	if (is_early_uv_system())
 		return;
 
-	if (cc_platform_has(CC_ATTR_GUEST_SNP_SECURE_TSC))
-		snp_secure_tsc_init();
+	snp_secure_tsc_init();
 
 	if (!determine_cpu_tsc_frequencies(true))
 		return;

-- 
Regards/Gruss,
    Boris.

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